What tongue can describe the heart of the divine mercy? What mind is not amazed by the riches of such great love? The psalmist was thinking of these riches of divine love when he said: My helper, I will sing a psalm to you. It is you, O God, who are my protector, my God, my mercy. Carefully weighing the labors surrounding our humanity, he called God his helper. He calls his “protector” the one who protects us in the midst of our present distress until we come to eternal rest. But bearing in mind that God sees our evil deeds and bears with them, that he puts up with our sins and still perseveres us for his rewards because of repentance, he could not just speak of God as being merciful but called him mercy itself, saying: My God, my mercy.
Let us then recall before our eyes the evil deeds we have done, let us consider with how much goodness God puts up with us, let us bear in mind the depth of his love. He is not only lenient toward our sins, but he even promises the heavenly kingdom to those who repent after sinning. Let each of us say from the very depths of our hearts, let us all say, My God, my mercy.
– St. Gregory the Great